The display module may have various defects after its manufacture, such as bright spots, dark spots and bright lines. For example, a bright line, for example, a tailing bright line, refers to a defect that a line having luminance higher than that of the surrounding area appears on one side of the display module when the display module displays a certain greyscale. When there are these defects in the display module, the display module has to be repaired to solve the problem.